The right-hander looks to bounce back from a rough debut with his new team and help the AL West-leading Rangers avoid a third consecutive loss Tuesday night against the Boston Red Sox at Fenway Park.Dempster (0-0, 15.43 ERA) went 5-5 with a 2.25 ERA in 16 starts for the Chicago Cubs this year, but allowed a season-high eight runs and nine hits -- two homers -- in 4 2/3 innings of a 15-9 win over the Los Angeles Angels on Thursday in his first start since Texas (63-45) acquired him two days prior."The most important thing was I kept the team in the ballgame and gave us a chance to win," Dempster told the Rangers' official website. "I'm not really used to that, giving up eight runs."Dempster allowed five hits in seven innings of a 3-0 win over Boston at Wrigley Field on June 15. This will be his first outing at Fenway since June 12, 2001, when he lost while pitching for the Marlins.He'll face a Boston squad that's looking for a third straight win after pounding out eight doubles in a 9-2 victory in Monday's series opener. Dustin Pedroia doubled three times while Jacoby Ellsbury and Carl Crawford each had two as the Red Sox (55-55) increased their major league-leading doubles total to 243.Boston had been outscored 39-12 while losing four of its previous five against Texas this season. The victory came hours after owner John Henry publicly gave first-year manager Bobby Valentine a vote of confidence despite the team's mediocre season."Our job is to go out and play," said first baseman Adrian Gonzalez, who went 3 for 5 with three RBIs. "It's us that are playing out there so the .500 record we're at right now, it's on us. It's not on Bobby."Crawford, who went 0 for 10 with five strikeouts during a three-game set at Texas last month, is 9 for 18 with eight RBIs in his last four games.The Red Sox now hand the ball to Jon Lester (5-9, 5.36), who is 0-4 with a 7.91 ERA in six starts since the beginning of July. Though he's posted a 10.62 ERA while losing his last four home outings, Lester showed improvement Thursday, when he gave up three runs and struck out seven with no walks in eight innings of a 5-0 loss to Minnesota at Fenway."I need to keep sticking with the process," Lester said. "Obviously, the results aren't there and a loss is a loss."The left-hander is certainly hoping for a better effort than his last versus the Rangers on April 17, when he gave up seven runs and walked four in two-plus innings of an 18-3 home loss. Lester had been 2-1 with a 2.97 ERA in five starts against Texas from 2009-11.Nelson Cruz -- 8 for 14 with two doubles, a triple and a home run against Lester -- had two doubles and a single Monday. He's a lifetime .415 hitter with eight doubles in 13 games at Fenway.Texas shortstop Elvis Andrus is expected to be in the lineup after missing Monday's game with a sore shoulder. The All-Star is 11 for 25 with seven RBIs in his last five games after going 1 for 19 in his previous five.